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We review the origin of millisecond pulsars and low-mass binary pulsars from low-mass X-ray binaries. Observations of such pulsars suggest that the existing evolutionary picture of low-mass X-ray binaries need major modifications. In particular, careful account has to be taken of the effect of the irradiation of the secondary star by high-energy radiation during the accretion phase, and by the radiation and particle wind from the pulsar after accretion ceases. Another element that has to be incorporated into this picture is the influence of accretion onto the neutron star and its spin evolution on its magnetic field strength.

In this article we review the arguments for and against the decay of the magnetic fields of neutron stars, in the light of most recent developments. We conclude that the field decay may only occur when the neutron star has been processed in an interacting binary. Some theoretical models for such an evolution are discussed.

Analyses of the statistics of pulsars and of pulsar-produced nebulae have, over the past several years, led to the conclusion that most pulsars are born spinning rather slowly, with periods in excess of 100 ms. In this note we examine whether a slow build-up of neutron star magnetic fields from very low initial values (~108 gauss) may provide a viable alternative to this, as has been suggested by some authors. We find that irrespective of whether the field grows or not, slow rotation of neutron stars at birth remains an inevitable conclusion.

We have detected a hydrogen recombination line, near 145 MHz, in the direction of the galactic centre with an optical depth of -2.7 ± 0.3 × 10-4. This is shown to arise in a nearby HII region with an electron density of 7 cm-3. The absence of any significant contribution to this line from the warm ionized medium (WIM) implies that it must have a temperature > 6700K and a filling factor >25%. If the temperature of the WIM is 8000K, then it must have a filling factor >60%.

From the extremely poor association between pulsars and supernova remnants, and the paucity of centrally filled synchrotron nebulae, presumably produced by active pulsars, we conclude that the majority of neutron stars must be born spinning rather slowly, with initial rotation periods ≳ 100 milliseconds.